Towards a miniature atomic scalar magnetometer using liquid crystal polarization rotator

CEA-LETI and CNES have successfully realized a helium-4 isotropic space-qualified magnetometer for the SWARM mission. The present paper reviews the progress made in the miniaturization of this isotropic optically pumped magnetometer. Sensor isotropy is provided by a liquid crystal polarization rotator that sets the pumping beam polarization at 90° with respect to the ambient magnetic field. It allows a continuous polarization rotation from 0° to more than 300° with response times sufficient for mobile or space applications. This rotator is non-magnetic and can be easily integrated close to the gas cell. The miniature sensor reaches a sensitivity of 10 pT/√Hz in a bandwidth from DC to 100 Hz.